In drilling wells for oil and gas exploration, the environment in which drilling tools and production components operate is at significant distances below the surface. Due to harsh environments and depths in which drilling in formations is conducted, enhanced efficiencies to post drilling operations are desirable. Such post drilling operations include making measurements downhole and communicating signals and/or data from such measurements to the surface at the well site.
The instrumentation of production strings using fiber optics based distributed systems such as distributed temperature sensing (DTS), distributed acoustic sensing (DAS), and other sensing systems based on for example interferometric sensing is well established. Optical fiber can be run on the outside of tubing and/or casing to the surface, where interrogators detect reflected light from the entire length of the fiber and/or single/multi point sensors. However, there are connections in the production string which prevent, or make difficult, fiber from being installed over the entire length of the string. In some cases, such difficulties may be overcome by using wet or dry fiber connects, although these connects have their own limitations. In other cases, such as with swivels, fiber can be wound around a collar like a spring so that it has some rotation flexibility, but this too has manufacturing and operational problems. There are also cases where sensors currently cannot be installed, such as in multi-lateral wells. In other cases, slips and packers clamp to the liners and prevent passage of the fiber.